This invention relates to methods of and apparatus for the manufacture of container liners. In particular, the apparatus relates to such methods and apparatus which are able to operate on at least a semi-automatic basis, with the aim of facilitating handling and product accuracy in the manufacture of such liners.
Liners for cargo containers, such as ISO box containers, are well-known and widely used for the bulk transport of flowable productsxe2x80x94for example granular materials including agricultural produce and chemicals. Such liners are usually made from plastics sheet material which is preformed into a tube, or from sheet material which is suitably folded and subsequently is seam-welded to make a tube. End panels for a liner are provided either by welding the plastics material in an appropriate manner or by bonding into the tube a separate end panel. Access openings are provided both for the loading and discharge of the liner, when in use, and also suitable arrangements must be made for the fixing of the liner in a container.
The manufacture of such a container liner tends to be somewhat labour intensive. Typically, a rolled web of the plastics material is supported adjacent a work-table and is drawn out over that work-table so that the required operations may be performed by operators reaching across the liner and using suitable tools, such as thermal welding apparatus. In view of the width of such a liner, these operations are not very easy to perform in the central region of the liner where, for example an access opening may have to be provided. A high degree of skill is required to ensure the welding or other bonding processes are carried out efficiently to provide a reliable joint which will not fail in use.
In U.S. Pat. No. 3,853,664, there is described apparatus for making bags on an automatic basis from a travelling web of plastics material folded to have inwardly-directed panels which when opened out define sides of the bag. The operations described in this specification serve to form the ends of the bag, by diagonally-extending welds.
In U.S. Pat. No. 3,069,303-A there is described a process and apparatus for converting a tube of thermoplastic flexible sheet material in an automatic matter to form an endwise closed container adapted to be filled with milk. A nozzle is secured to a side wall of the container using a floating mandrel within the tube, to act as a counter force for a piercing and heat-sealing operation. The mandrel is maintained in a substantially fixed position by means of cradle roll pairs acting through the walls of the tube.
A principal object of the present invention is to provide both a method of and apparatus for the manufacture of relatively large-scale cargo container liners, which are suitable for at least partial automation, so as to reduce the labour intensive nature of the known cargo container liner manufacturing processes whilst at the same time giving at least as good and consistent reliability for the manufactured liners, as is achieved by the known manual processes.
According to one aspect of this invention, there is provided a method of manufacturing a bulk transport cargo container liner from a web of folded-flat gussetted sheet plastics material having over-lying upper and lower layers between the long edges of which are respective pairs of inwardly-folded gusset panels, which method comprises the steps of:
extending the web over a work-area and arranging a shuttle between the layers of the material, which shuttle extends substantially across the width of the web so as to hold separated layers of the plastics material above and below the shuttle and with the side edge margins of the shuttle located between the upper layer and the adjacent inwardly-folded gusset panels;
defining in the web a first end region for the finished liner;
advancing the web over the work-area whilst applying a force to the shuttle through the plastics material so as to maintain the shuttle substantially stationary with respect to the work-area, until a part of the material corresponding to a required location for an attachment of the finished liner over-lies the shuttle;
bonding to the plastics material at said location an attachment for the liner, using the shuttle to provide a counter-force for bonding operation;
further advancing the web over the work-area whilst continuing to maintain the shuttle stationary with respect to the work-area, until the required length of plastics material for the finished liner extends beyond a closure station downstream of the shuttle;
providing at the closure station a pair of separator boards disposed one each side of the web and each projecting between the folded material defining the gusset panels thereby separating the upper and lower gusset panels;
effecting at the closure station upper and lower weld seams across the width of the web thereby to join the upper and lower layers to the respective upper and lower gusset panels with the weld seams on each layer being in a generally V-shaped configuration thereby to form an end panel at a second end region of the liner; and
cutting the plastics material from the web so at least partially completing the liner.
According to another, but closely related, aspect of the present invention, there is provided apparatus for the automated production of a bulk transport cargo container liner, comprising:
a holder for a reel of liner-forming folded-flat gussetted sheet plastics material web having over-lying upper and lower layers between the long edges of which are respective pairs of inwardly-folded gusset panels;
means to draw the web from a held reel thereof and advance the web over a work-area;
a shuttle adapted for location between the layers of the web, which shuttle extends substantially across the width of the web to hold separated the layers of the plastics material above and below the shuttle with the side edge margins of the shuttle located between the upper layer and the adjacent inwardly-folded gusset panels, the shuttle being disposed over the work-area and being provided with means to maintain the shuttle substantially stationary during advancement of the web;
gripping means for an attachment for the liner and arranged to move said attachment into engagement with the web at a location where the attachment is to be secured to the liner;
a plastics bonder adapted to effect a bonding operation of the engaging surfaces of the web and the attachment;
a pair of separator boards provided at a closure station, one each side of the web and each projecting between the folded material defining the gusset panels, thereby separating the upper and lower gusset panels;
seam-welding apparatus disposed at the closure station to effect upper and lower weld seams across the width of the web thereby to join the upper and lower layers to the respective upper and lower gusset panels with the weld seams on each layer being in a generally V-shaped configuration thereby to form an end panel at a second end region of the liner; and
a web-cutter to sever a length of web material drawn from the reel, so as at least partially to form the liner.
It will be appreciated that both aspects of this invention allow the manufacture of a cargo container liner from a web of folded-flat sheet plastics material, on at least a semi-automated basis if not a fully-automated basis. The plastics material may be pre-formed to be a tube, in which case it may have inwardly-folded gussets extending along the length of both sides of the flat tube. Such tubes are already used for the manufacture of liners and typically the inner edges of the gussets more or less meet in the central region of the tube, when flat. In the alternative, the sheet may be in the form of an elongate web simply folded to provide two overlying layers with adjacent side edges and which edges may be seam-welded together during the manufacturing process to provide the main part of the liner, when completed.
In the method, the shuttle is located between the layers of the web, so as to permit the required manufacturing operations to be performed on one layer (usually the upper layer) without affecting the underlying layers. Such operations may include thermal welding to the upper layer, and the cutting of openings through the upper layer. As the web is drawn out over the work-area, typically from a reel of the plastics sheet material arranged at one end of the work-area, the shuttle must be maintained stationary and so in effect run through the moving web. This may be achieved by the interaction of magnetic materials respectively on the shuttle and associated with the work-area. For example, a plurality of permanent magnets may be provided on the shuttle and a like plurality of magnets (either permanent magnets or electromagnets) may be provided on the work-area in the same physical array, whereby each shuttle magnet may directly co-act with a corresponding magnet on the work-area.
In an alternative arrangement, the shuttle is provided with at least one roller and there is at least one further roller mounted externally of the web to interact with the shuttle roller through a layer of the sheet plastics material, thereby to maintain the shuttle substantially stationary during advancement of the web.
As with the known manual manufacturing techniques, the end panels of the liner may be defined by suitably profiled and positioned welds or other bonds formed across the web and any gussets formed therewith, or by separate panels let into the web and bonded in position thereby to define the liner ends.
In a typical manufacturing method, a plurality of attachments are secured to the plastics material forming the liner. For example, such attachments may comprise fixing devices, such as suspension or retention devices, for the liner, when in use. Alternatively, or in addition, the attachment could comprise an access-pipe, in which case an opening may be cut through the liner at the required location for the access-pipe, before or after the bonding of the access-pipe to the plastics material. In this case, the shuttle may act as a counterforce for the cutting step which forms the opening, as well as for the bonding step. When there is more than one attachment, these may be spaced along the length of the liner, which is correspondingly advanced step-wise along the work-area.
The bonding operation securing each attachment to the liner may comprise one of an adhesive bonding step, a chemical fusion step or a thermal welding step.
In one embodiment, the underside of the shuttle is provided with at least one running roller which runs on a surface of the work-area, through the or each underlying layer of the plastics sheet material below the shuttle. Preferably, a plurality of such rollers are provided, to support the entire weight of the shuttle. Each such roller may be in the form of a caged freely-rotatable ball, able to roll in any direction in the plane of the work-area, thereby to facilitate centralisation of the shuttle as the web is advanced.
A pair of lower rollers may be provided in the work-area for each roller of the shuttle, whereby each shuttle roller is located by and runs on its associated pair of lower rollers, with the web running between the lower rollers and the shuttle rollers. Such lower rollers may be free-running, or could be power-driven, to facilitate advancement of the web. In either case, the primary positioning of the shuttle may still be the use of magnets, as aforesaid.
In another embodiment, the shuttle rollers may be power-driven by a remote control system responsive to the drawing of the web over the work-area; in this way, the shuttle may be maintained stationary during advancement of the web. Power may be supplied to such a remote control system by an electrical, pneumatic, hydraulic or other power-recharging operation which connects with the shuttle when stationary for the bonding of an attachment to the web. Alternatively, an optical or inductive power coupling system from an external (of the web) power source may be used.
In a case where the web is a simple folded plastics sheet material with adjacent long edges, the shuttle may be maintained stationary by means of an arm connecting the shuttle to a stationary part of the apparatus, which arm extends out of the web, between the adjacent long edges thereof. In this case, the long edges may be joined downstream of the arm by means of a continuous seam-welding operation, to form a complete liner.
As mentioned hereinbefore, the attachment may be an access-pipe leading to the interior of the liner. Such an access-pipe may comprise a pipe of flexible plastics material cut from a web thereof. The end portion of such a pipe may be stretched to form a flange which is engaged with a corresponding surface of the plastics material of the liner around an opening formed therein, the engaging surfaces then being bonded together. Where such bonding is performed by welding, the shuttle itself may provide a thermal source for the bonding operation, or a separate welding head may be provided for this purpose.
The web for forming into the liner is a tube having, when folded flat, inwardly folded gussets, the shuttle extending across the width of the web to the fold lines at the edges of the upper layer of the web. The shuttle may have gusset boards which are adjustable with respect to the central part of the shuttle, such that the outer edges of the boards locate closely adjacent the edges of the upper layer of the web. This permits the accurate location of the shuttle with respect to the liner, and also the securing of attachments to the side edge regions of the upper layer of the web forming the liner, but not to the underlying layers.